Lumbar spinal stenosis is known as a common and severely disabling condition affecting older persons. Our recently completed R-01 grant has challenged the standard for diagnosis by showing that stenosis on magnetic resonance imaging (MRI) has little to do with the clinical syndrome of stenosis. Electromyography (EMG) was shown to be a useful test. However the study did not look claudication (leg pain on walking), an extreme symptom of stenosis. Claudication can also occur in vascular disease. It is important clinically and scientifically to positively differentiate these two causes of claudication. Specific Aims: Determine the ability of MRI and EMG to separate persons with neurogenic claudication from persons with vascular claudication, and asymptomatic controls. Hypotheses: 1. The presence and severity of neurogenic claudication relate to both MRI spinal canal geometry and electrodiagnostic abnormalities. 2. Neurogenic claudication can be discerned from vascular claudication by use of MRI and EMG findings. Research design: Prospective, masked, controlled study. Methods: Three groups of persons aged 55-80, including asymptomatic volunteers, persons with definitive vascular claudication, and persons with neurogenic claudication, will be obtained by screening persons from the community, vascular surgery clinic, and spine program;having them undergo examinations by a vascular and neurosurgeon as well as ankle-brachial index (ABI) testing. Candidates with consensus diagnosis will undergo masked EMG and MRI scans, ambulation questionnaires, a 6 minute ambulation test and a 5 day activity monitor evaluation. We will determine sensitivity, specificity, and discriminant value of MRI (minimum canal diameter) and EMG (composite fibrillation score) in separating those with isolated neurogenic claudication from those with vascular claudication and asymptomatic controls. PUBLIC HEALTH RELEVANCE. The surprising result of our previous NIH funded study shows that 'spinal stenosis'on magnetic resonance imaging (MRI) scans does not separate people with 'spinal stenosis'--a sometimes severely disabling disease that is treated with surgery--from persons with plain old back ache or no pain at all. Electromyography (EMG) was successful, but since the study could be criticized for not including many people with severe stenosis, this proposal looks at EMG and MRI scans in those with the most severe stenosis complaint (claudication, or leg cramping with walking), in comparason to persons with artery disease in the legs, which is another cause of claudication. The results will help doctors avoid unnecessary surgery and help scientists to understand more about how spinal stenosis disables so many older people.